Pest risk analysis in Europe - how can risks of invasive alien species be assessed and managed?

German. Pest risk analysis (PRA) is a tool used in plant health to assess risks of quarantine pests or other organisms harmful to plants and to identify options for their management. Standards of the International Plant Protection Convention (IPPC) and the European and Mediterranean Plant Protection Organisation (EPPO) are available to facilitate the procedure of PRA. Recent amendments of these standards allow a better analysis of risks posed by plant pests to biodiversity and the environment. By this, the regulation of species that threaten biodiversity (invasive alien species) can be technically justified according to the Sanitary and Phytosanitary Agreement under the World Trade Organisation. At present, in particular risks of invasive alien plants are in the focus of adapting PRA in Europe. There are several differences between the assessment and management of pests directly harmful to cultivated plants and pests threatening biodiversity or the uncultivated environment. In many cases, the identification of (potential) invasiveness is very difficult. For the assessment of economic importance of environmental risks, several methodologies are provided that differ from the conservative economic assessment. In contrast to the 'traditional plant pests', which are introduced unintentionally, alien plants are usually introduced intentionally. Planting them into intended habitats usually does not pose any problems, only very few species spread into unintended habitats and have adverse effects. For selection of management options a differentiated approach is necessary, including the prohibition of introduction of significantly risky plants and the obligation for specified requirements to restrict their spread.